I have a Maine Coon who loves playing in water. He steps in his water bowl and sucks the water off his paw, then turns the bowl upside down (I don't know why.) The water bowl sits on a plastic mat and he laps the water that he spilled off the mat. I pour water directly on the mat for him, which kind of works. I finally thought to put a big towel under the mat, because this is in a carpeted room and the carpet was getting ruined.

I worry that he's not getting enough water and his whole mess-making process means there's no water left for his brother. The Maine Coon used to only drink from the bathroom tap, but now he can't be bothered.
I'm hesitant to get a fountain because who knows what kind of havoc he'd wreak with it. He's really strong and moves things all by himself all the time.

Anyone have any other ideas, besides encouraging him when he drinks water out of the bowl normally? I tried putting a bowl in the sink and he wasn't interested.

I know the ones Barkingdog means. It's a water bowl that has a bigger upside down bottle attached to its base. In proper words like BD said it's a reservoir.
It doesn't have a motor, doesn't make any noise and they're affordable. Ive seen them in Wal Mart even.
I think it's a great idea. Your cat will still pkay with the water but it's unlikely he'll knock it over and there will be plenty for kitty brother.
+1 To that idea